Permanently set bridge plug



Nov. 15, 1966 H. J. URBANOSKY PERMANENTLY SET BRIDGE PLUG Filed March 11, 1964 IN VEN TOR.

United States Patent 3,285,343 PERMANENTLY SET BRIDGE PLUG Harold J. Urbanosky, Houston, Tex., assignor to Schlumberger Well Surveying Corporation, Houston, Tex., a corporation of Texas Filed Mar. 11, 1964, Ser. No. 351,079 7 Claims. (Cl. 166-134) This invention relates to a bridge plug for use in packing-off a well bore, and, more particularly, to a bridge plug designed to be set permanently in place within a cased well bore.

A bridge plug typically includes a mandrel on which is mounted an elastomenic sleeve or packing element disposed between sets of reversely directed, extendible, slip elements operatively mounted around tapered expander elements, with the slip elements being releasably held thereon in an imperative or retracted first position, and a body lock which maintains the elements in an operative second position. Setting of such a bridge plug in a well bore is conventionally accomplished by use of a setting tool which applies increasingly greater and oppositely directed forces to the bridge plug in such a manner that the packing element is expanded into sealing engagement and the slip members are extended into engagement with the well casing to anchor the bridge plug in place at a particular depth.

Heretofore, it has been conventional to utilize various arrangements of frangible shear rings or pins for releasably holding the slip members on the expanders in a retracted first position to allow the bridge plug to be easily positioned in a well bore. These shear members are generally arranged in such a manner that, as the forces applied by the setting tool increase, the members will fail in a particular order and release the slip members in accordance with a predetermined sequence.

Usually, in setting a typical bridge plug with a conventional wireline setting tool, at least one of the slip members is released and dragged along the casing before the packing element has been completely displaced, which dragging can break some of the casingengaging teeth around the slip members. Furthermore, with a wireline setting tool having a tension-stud release, it will be appreciated that such dragging can reduce the degree of expansion of the packing element should the additional drag cause the tension-stud to release the setting tool before the packing element has been fully set. 7

With those bridge plugs having slip members composed of a group of frangibly connected segments mounted around the expanders, upon failure of the frangible connections the individual segments are then free to move independently of their companion segments. Thus the individual segments are no longer coordinated and will not necessarily maintain their initial angular spacing or axial alignment. Accordingly, when finally engaged with the casing, the segments may be tilted and erratically spaced which distributes the anchoring forces unequally around the casing. Moreover, when such a bridge plug is used in an inclined well here, one side of the slip members will lay against the casing, and, when the slip members are released, the segments at the opposite or upper side of the slip members must advance [further along the expander before engaging the casing than those initially resting against the casing. Thus, the bridge plug will usually remain eccentrically disposed which may prevent the packing element from sealing completely and uniformly around its periphery.

Conventional shear pins have not been entirely satisfactory for other reasons as well. For example, when a large number of bridge plugs are mass-produced, it is 3,285,343 Patented Nov. 15, 1966 "ice I fore reassembling and inserting the pins.

e forth with particularity in the appended claims.

Furthermore, it is not uncommon for the sudden shock which is imparted to a bridge plug when a shear member fails to crack a cast component of the bridge plug. It has also been found that a shear member will sometimes break irregularly and leave a projection which retards or even prevents the free relative movement of the elements after they are supposedly freed.

Accordingly, it is a particular object of the present invention to provide a reliable bridge plug assembly in which shear member connections between the slip members and expander elements are eliminated.

It is a further object of the invention to .provide means for coordinating the extension of slip members whereby the individual segments of the slip members will maintain a uniform angular spacing and remain axially aligned as they are being extended into anchoring engagement with a well casing.

I These and other objects of the present invention are obtained by a bridge plug which includes, among other things, expansible restraining means for yieldably holding extendi-ble slip members in a first retracted position and allowing the slip members to be controllably extended radially into anchoring engagement with the casing with little or no longitudinal movement of the members across the casing.

The bridge plug of the present invention includes a central mandrel carrying at each end thereof opposed sets of frusto-conical slip expanders operatively engaged with extend-ible slip members. An elastomeric packing element is disposed between the opposed slips and expanders with its ends preferably being con-fined within expansible antiextrusion members. A body-lock arrangement is provided for maintaining the members in their operative positions after the setting tool has been disengaged.

The extendible slip members are yieldably retained in a retracted position by one or more expansible circumferential band members so arranged that when the setting forces reach a predetermined magnitude, the bands will stretch without breaking so that the slip members will be uniformly and controllably extended radially into engagement with the casing in a particular predetermined sequence.

The novel features of the present invent-ion are set The present invention, both as to its organization and manner of operation together with further objects and advantage thereof, may best be understood by way of illustration and example of certain embodiments when taken in conjunction with the ac'ompanying drawings, in which:

FIG. 1 illustrates a bridge plug, partly in section employing one arrangement of the novel expansible sliprestraining members of the present invention;

FIG. 2 is a section taken along the lines 22 of FIG. 1; and

FIG. 3 is a view showing the bridge plug of FIG. 1 set into sealing and anchoring engagement within a well casing.

Turning now to FIGS. 1 and 2, one embodiment of a bridge plug 10 constructed in accordance with the principles of the invention is shown with portions thereof in section for purposes of greater clarity. The mandrel 11 is an elongated cylindrical member around which is slidably mounted an elastomeric packing sleeve or element 12 which has its ends confined by oppositely directed conventional lower and upper expansible anti-extrusion rings 13, 14, respectively. Oppositely directed lower and upper Washer or spacer members 15, 16 are slidably mounted around mandrel 11 at opposite ends of the anti-extrusion rings 13, 14, with each washer having an inwardly directed, tapered, surface 17, 18 oomplementarily engaged with the outer faces of the anti-extrusion ring-s. Lower and upper extendible slip members 19, 20, as will be later described in detail, are slidably disposed around the mandrel 11 with'their base portions 21, 22 respectively engaged with the flattened outer ends 23, 24 of lower and upper washer members 15, 16. Lower and upper frusto-conical slip-expander members 25, 26 are oppositely directed and slidably mounted around the mandrel 11 with their tapered surfaces 27, 28 respectively engaged within complementarily formed tapered surfaces 29, 30 of lower and upper slip members 19, 20. The lower slip-expander member 25 rests against an upwardly facing shoulder 31 around the lower end of mandrel 11.

Upper slip-expander member 26 has an upwardly direc ted and outwardly diverging tapered surface 32 forming an annular recess 33 for receiving a complentarily tapered split-nut 34. Split-nut 34 has ratchet teeth 35 around its axial bore cooperatively engaged with downwardly facing ratchet teeth 36 cut around the upper end of mandrel 11. A spring member 37 is operatively engaged between the upper end 38 of split-nut 34 and a snap-ring 39, which is in turn held against a downwardly facing circumferential shoulder 40 formed around the upper end of recess 33. Spring member 37 is preferably an assembly of two opposed springs, with each spring consisting of a single flat ring having resilient projecting tabs interlocked with the tabs of the other spring. These springs, when nested together, make a compactly arranged spring member with flattened annular end surfaces.

The upper end of upper slip-expander member 26 has a reduced outer-diameter portion 41 providing an upwardly facing shoulder 42 which is sized and arranged for receiving the lower end of the outer sleeve or pushing member of a conventional setting tool (not shown). External threads 43 are provided around the upper end of mandrel 11 for coupling to the inner mandrel or pulling member of the set-ting tool. A reduced-diameter or necked portion 44 near the upper end of mandrel 11 is sized to fail whenever oppositely directed longitudinal forces of a predetermined magnitude are applied in the well-known manner by the setting tool.

The extendible slip members :19, 20 consist of a plurality of individual sectorially formed slip segments 45, 46, which segments have a plurality of hardened casingengaging teeth 47, 48 along their outer arcuate faces. Slip segments 45, 46 are symmetrically grouped at regular intervals around the slip-expanding members 25, 26, respeotively, with each group of segments being yieldably retained in engagement with tapered surfaces 27, 28, by one or more expansible bands 49-52 of a ductile material, such as brass, which encircle and confine the individual segments. It will be understood, of course, that th ugh a single expansible band on each slip member quid be adequate, it is preferred to place an expansible band around each end of the slip members 19, 20 to i ensure that all segments of a slip member act in unison aswell as to provide a greater degree of control over the teral movement of the segments as the slip-expanding members are moving to expand the slip members.

Itiwill be appreciated that by varying the dimensions selecting the ductile material of the annular restraine 'bers 49-52, the strength of these bandscan be gulated so that they will not yield until a rede mined-magnitude is applied thereto,

of stretching the bands sufiicientslip segments to extend radially cut with the casing wall 53 (FIG. illsibe realized that so long as the 2' hold the slip segments'in their initial retracted position (FIG. 1), the longitudinally directed forces applied by a setting tool to the bridge plug 10 will act through the slip-expanding members 25, 26 and slip members 19, 20, respectively, on the opposite ends of the packing element 12. The element 12 will of course begin expanding into sealing engagement with the casing 53 in response to the increase of the setting forces, with the degree of expansion of the element at a particular magnitude of forces being governed by the properties of the elastomeric material selected and the dimensions of the element.

Accordingly, in the present invention, the ductile restraining members 49-52 are sized where they will not stretch until the setting forces have increased to a predetermined magnitude, which magnitude may be less than, equal to, or greater than the magnitude of force required to completely expand the packing element 12 against the casing 53. Thus, it will be understood that by regulating the strength of the restraining members 49-52, the degree of expansion of the packing element 12 is closely controlled.

Restraining members 49-52 are preferably sized and proportioned to restrain the outward extension of the slip members 19, 20 until such time that packing element 12 has a least been substantially expanded against the casing 53. Thus, by properly correlating the amount of force required to stretch the restraining bands or members 49- 52 to the amount of force required to displace the packing element 12, the slip segments 45, 46 can be delayed from engaging the casing 53 until the packing element 12 has first been displaced a predetermined amount during the setting operation.

It is of equal importance to the invention that the expansible bands 49-52 are arranged to stretch without breaking. By selecting a ductile material for the bands and by sizing them properly, the bands will stretch circumferentially which will allow the individual segments 45, 46 to move outwardly only in unison. Thus, the restraining influence provided by the bands as they stretch will maintain the axial alignment and angular relationship of the individual segments as slip-expanding members 25, 26 drive the segments outwardly against the casing 53.

It should also be noted that by arranging restraining members 50, 52 on the inward side of the slip members 19, 20, whenever the slip members are engaged with the casing 53, the annular restraining members 50, 52 completely close any sectorial spaces remaining between the individual segments 45, 46 which otherwise would exist between the outer periphery of the washer members 15, 16 and the casing wall 53. Thus, annular restraining members 50, 52 also serve as additional anti-extrusion members should the elastomeric packing element 12 not be wholly confined by anti-extrusion rings 13, 14.

It should be further noted that by sizing restraining members 49-52 .to prevent the full extension of the slip members 19, 20 until the packing element 12 has been substantially displaced against the casing 53, the hardened teeth 47, 48 of the slip members will not contact the casing until the movable members of the bridge plug have nearly reached their final positions. Thus, when the slip segments 45, 46 do engage the casing, it will be appreciated that the teeth 47, 48 are not dragged across the casing walls but instead remain substantially where they first engage the casing.

When the bridge plug 10 of FIG. 1 is to be used, a conventional setting tool .(not shown) is attached to the upper end of bridge plug 10. The pulling member or inner mandrel (not shown) of the setting tool is threadedly attached to threads 43 at the upper end of mandrel 11 and the pushing member or outer sleeve (not shown) of the setting tool is cooperatively engaged with the upwardly facing shoulder 42 of upper slip-expander member 26.

When the bridge plug has been correctly positioned within a cased well bore, the setting tool is then operated in the conventional manner to pull mandrel 11 and lower slip-expander member along with slip member 19 upwardly as the setting tool sleeve forces upper slip-expander member 26 and slip member 20 downwardly. As the upper slip member 20 and slip-expander members 26 advance toward the lower slip member 19 and slip-expander member 25, it will be appreciated that gradually increasing and oppositely directed setting forces will be applied from the setting t-ool through the slip members 19, '20 and spacer members 15, 16 against the opposite ends of the packing element 12, which forces Will first begin foreshortening and displacing the packing element radially outwardly into sealing engagement with the casing wall 53.

When the setting forces have increased to a predetermined magnitude, restraining members 49-52 then yield and being to slowly stretch, which stretching then allows the tapered slip-expander members 25, 26 to move inwardly relative to the slip members 19, 20 and being extending the individual slip segments 45, 46 radially outwardly in unison as they slide along tapered surfaces 27, 28. When restraining members 49-52 have stretched sufficiently, the hardened teeth 47, 48 of the individual slip segments 45, 46 will contact the casing 53 and the continued inward travel of the slip-expander members 25, 26 relative to the segments will subsequently drive the hardened teeth radially into the casing.

When the setting tool is actuated and the mandrel 11 first begins to travel upwardly, ratchet teeth 36 on the mandrel will slide under ratchet teeth on split-nut 34 to expand the split-nut. Accordingly, split-nut 34 is free to alternately expand and contract, and each time it expands, it will begin sliding relatively upwardly and outwardly along the tapered surfaces 32 of upper slip-expander member 26. As split-nut 34 begins to slide upwardly, however, spring member 37 is compressed and then expands to drive the split-nut inwardly and downwardly to force ratchet teeth 35 into engagement with the next group of ratchet teeth 36 around the mandrel. This alternate compression and expansion of spring member 37 tends to drive split-nut 34 downwardly while preventing any backlash or retrograde movement of the packing element. It Will be appreciated, therefore, that the split-nut 34 will be continuously driven over the lowermost ratchet teeth 36 of the mandrel that the ratchet teeth 35 can engage.

After the bridge plug has been completely set in anchoring and sealing engagement with the casing, the setting tool forces continue to increase until weakened portion 44 of mandrel 11 fails, which failure will release the mandrel from the setting tool and allow the setting tool to be retrieved in the conventional manner. Thus, when bridge plug 10 is finally anchored and the setting tool disengaged, it will be appreciated that the bridge plug will effectively resist either upwardly or downwardly directed forces.

With any bridge plug having an elastomeric packing element, it will be appreciated that after the element is set, longitudinally directed forces on the packing element will proportionately increase the radial loading of the element against the casing. Thus, when there is a pressure differential across a bridge plug engaged in a well casing, well pressure is applied on the annular cross-sectional rea of the packing element which increases the casing loading. This same well pressure is also applied on the circular cross-section of the mandrel; and with a conventionally arranged bridge plug, the resulting force on the mandrel is transmitted through the packing element to the slip member opposing forces in that direction, which pressure force further increases the radial loading of the packing element against the casing.

It should be noted that in contrast to conventionally arranged bridge plugs, in the bridge plug 10 of the present invention, the upper slip member 20 is provided with downwardly facing casing-engaging teeth 48 whereas the teeth 47 on the lower slip member 19 are directed upwardly. Accordingly, it will be appreciated that the upper slip member 20 will primarily resist downwardly directed loads and that the lower slip member 19 will primarily resist upwardly directed loads.

It will be appreciated, therefore, that with the bridge plug 10 of the present invention, longitudinally directed loads on the mandrel 11 are not transmitted to the packing element 12 but are instead imposed directly on the slip member opposing forces acting in that direction. For example, an upwardly directed load on the mandrel is directly transmitted from the mandrel 11 and lower slip expander member 25 into lower slip member 19, which is engaged with the casing in such a manner as to oppose such upwardly directed forces. Similarly, a downwardly directed force is transmitted directly to the upper slip member 20. Thus, once the bridge plug 10 of the present invention is set, pressure forces acting on the mandrel 11 will not be transmitted to the packing element 12 which accordingly reduces the likelihood that additional loading of the element might bulge or split the casing or perhaps crack cement behind the casing 53.

It Will be further appreciated that the expansible retaining bands 49-52 of the present invention may be employed with equal success on conventionally arranged bridge plugs where the relative positions of the expanders and slip members are reversed from that shown in FIG. 1. In such instances, where the expanders are abutted against opposite ends of the packing element with the slip members being carried on the outer ends of the expanders, the expansible bands may be advantageously utilized in several manners. For example, with a conventional bridge plug, the upper slip member has upwardly directed teeth and is usually extended into anchoring engagement before the lower slip member. Then, as the setting tool forces continue to increase, the packing element is radially displaced and foreshortened with the upper slip member remaining fixed against the casing to serve as a back-up. The lower slip member is finally allowed to extend as it is pulled upwardly until failure of the tension-stud releases the setting tool.

Where this particular sequence of operation is desired, a relatively weak restraining band or a set of such bands arranged around the upper slip member would be proportioned to stretch under a fairly light load which will allow the upper slip member to anchoringly engage the casing before the packing element is expanded. Another stretch band or a set of bands arranged around the lower slip member would be proportioned to withstand a considerably higher force. Accordingly, extension of the lower slip member would be controllably delayed until the packing element has been substantially displaced or even until it has been completely displaced against the casing. It will be appreciated, therefore, that with this particular arrangement, the restraining bands on the lower slip member will prevent the teeth of the lower slip from engaging the casing until the bridge plug has been shifted to substantially its final position. Thus, with this controlled delay, the teeth on the lower slip member will be dragged along the casing at best only a short distance, if at all. In any event, the restraining influence of the bands as they are stretched will ensure that all slip segments maintain a uniform angular relationship as well as remain axially aligned as they are being extended into engagement with the casing.

Accordingly, it will be appreciated that a bridge plug constructed in accordance with the present invention will be suitable for high-pressure service in well conduits with the slip members carrying most of the additional loads imposed thereby. Furthermore, the segments of the slip members will be extended in unison and maintained in a uniform disposition to provide a uniform loading against the casing as Well as to ensure that the bridge plug is centralized Within the casing. The ductile restraining bands of the present invention also eliminate the necessity for the various shear member arrangements wherever they have been used heretofore for holding slip members in a retracted position around their respective slip-expanding tended first position.

members. Thus, as a setting tool is setting a bridge plug employing principles of the present invention, the slip members will move positively totheir anchoring positions without any sudden shock being imparted to the bridge plug as is the case when a conventional shear member connection fails.

While particular embodiments of the present invention have been shown and described, it is apparent that changes and modifications may be made without departing from this invention in its broader aspects .and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

What is claimed is:

1. In a packer device having a central body member with an expansible packing element operatively mounted and arranged thereon for expansion into sealing engagement with a well bore in response to a force of a first predetermined magnitude; a frusto-conical slip-expanding member on said body member adjacent one end of said packing element; an extendible slip member complementarily fitted and slidably mounted around said slipexpanding member and arranged to be expanded outwardly thereby from a retracted first position into anchoring engagement with a well bore at an extended second position in response to relative advancement of said slipexpanding member into said slip member; and means cooperating with said packing element and said members for expanding said element and said slip member into engagement with a well bore, the improvement comprised of: means for releasably retaining said slip member in said retracted first position including an expansible ring member of a ductile material around a portion of said slip member, said ring member being stretchable in response to a force of a second predetermined magnitude greater than said first magnitude to release said slip member and allow said slip member to expand into said extended second position after said packing element has been expanded.

2. In a packer device having a central body member with an expansible packing element operatively mounted and arranged thereon for expansion into sealing engagement with a well bore in response to a force of a first predetermined magnitude; first and second oppositely directed frusto-conical slip-expanding members respectively mounted on said body member adjacent opposite ends of said packing element; first and second extendible slip members respectively complementarily fitted and slidably mounted around said slip-expanding members and arranged to be expanded outwardly thereby from a retracted first position into anchoring engagement with a well bore at an extended second position in response to relative advancement of each of said slip-expanding members into its respective slip member; and means cooperating with said packing element and said members for expanding said element and said slip members into engagement with a well bore, the improvement comprised of: means for releasably retaining one of said slip members in said retracted first position including an expansible ring member of a ductile material around a portion of said one slip member, said ring member being stretchable in response to a force of a second predetermined magnitude greater han said first magnitude to release said one slip member and allow said one slip member to expand into said ex- 3, In a packer device having a central body member with an expansible packing element operatively mounted and arranged thereon for expansion into sealing engagement with a well bore in response to a force of a first predetermined magnitude; first and second oppositely directed frusto-conical slip-expanding members respectively mounted on said body member adjacent opposite ends of said packing element; first and second extendible slip members respectively complementarily fitted and slidably mounted around said slip-expanding members and arranged to be expanded outwardly thereby from a retracted first position into anchoring engagement with a well bore at an extended second position in response to relative advancement of each of said slip-expanding members into its respective slip member; and means cooperating with said packing element and said members for expanding said element and said slip members into engagement with a well bore, the improvement comprised of: means for releasably retaining said slip members in said retracted first position including first and second expansible ring members of a ductile material respectively mounted around said first and second slip members, said ring members being stretchable respectively in response to forces of a second and third predetermined magnitude to release said slip members and allow said slip members to expand into said extended second position.

4. The apparatus of claim 3 wherein said second predetermined force magnitude is greater than said first predetermined force magnitude.

5. The apparatus of claim 3 wherein said second prede termined force magnitude is greater than said first predetermined force magnitude and said third predetermined force magnitude is less than said first predetermined force magnitude.

6. The apparatus of claim 3 wherein said second and third predetermined force magnitudes are equal to one another and greater than said first predetermined force magnitude.

7. In a well tool having a body, slip and expander means on said body operable in response to longitudinally directed setting forces applied thereto for anchoring the tool in a well conduit, said slip means being movable outwardly of said body, and a packing means on said body expandable in response to said setting forces for packing oil the well conduit, the improvement comprising, in combination, annular restraining means encircling and engaging said slip means, said restraining means being constructed of a ductile, stretchable material with a prede termined yield strength such that the operation of said slip and expander means can be delayed until said packing means can be substantially expanded and, after yielding, said restraining means can function to control outward movement of said slip means.

References Cited by the Examiner UNITED STATES PATENTS CHARLES E. OCONNELL, Primary Examiner.

D, H, BROWN, Assistant Examiner, 

7. IN A WELL TOOL HAVING A BODY, SLIP AND EXPANDER MEANS ON SAID BODY OPERABLE IN RESPONSE TO LONGITUDINALLY DIRECTED SETTING FORCES APPLIED THERETO FOR ANCHORING THE TOOL IN A WELL CONDUIT, SAID SLIP MEANS BEING MOVABLE OUTWARDLY OF SAID BODY, AND A PACKING MEANS ON SAID BODY EXPANDABLE IN RESPONSE TO SAID SETTING FORCES FOR PACKING OFF THE WELL CONDUIT, THE IMPROVEMENT COMPRISING, IN COMBINATION, ANNULAR RESTRAINING MEANS ENCIRCLING AND ENGAGING SAID SLIP MEANS, SAID RESTRAINING MEANS BEING CONSTRUCTED OF A DUCTILE, STRETCHABLE MATERIAL WITH A PREDETERMINED YIELD STRENGTH SUCH THAT THE OPERATION OF SAID SLIP AND EXPANDER MEANS CAN BE DELAYED UNTIL SAID PACKING MEANS CAN BE SUBSTANTIALLY EXPANDED AND, AFTER YIELDING, SAID RESTRAINING MEANS CAN FUNCTION TO CONTROL OUTWARD MOVEMENT OF SAID SLIP MEANS. 